ftrace,kdb: Allow dumping a specific cpu's buffer with ftdump

In systems with more than one processor it is desirable to look at the
per cpu trace buffers.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
CC: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 27 insertions, 10 deletions

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 44cbda25b0a5..7b8ecd751d93 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -17,7 +17,7 @@
 #include "trace.h"
 #include "trace_output.h"
 
-static void ftrace_dump_buf(int skip_lines)
+static void ftrace_dump_buf(int skip_lines, long cpu_file)
 {
         /* use static because iter can be a bit big for the stack */
         static struct trace_iterator iter;
@@ -44,13 +44,20 @@ static void ftrace_dump_buf(int skip_lines)
         iter.iter_flags |= TRACE_FILE_LAT_FMT;
         iter.pos = -1;
 
-        for_each_tracing_cpu(cpu) {
-                iter.buffer_iter[cpu] =
+        if (cpu_file == TRACE_PIPE_ALL_CPU) {
+                for_each_tracing_cpu(cpu) {
+                        iter.buffer_iter[cpu] =
                         ring_buffer_read_prepare(iter.tr->buffer, cpu);
-                ring_buffer_read_start(iter.buffer_iter[cpu]);
-                tracing_iter_reset(&iter, cpu);
+                        ring_buffer_read_start(iter.buffer_iter[cpu]);
+                        tracing_iter_reset(&iter, cpu);
+                }
+        } else {
+                iter.cpu_file = cpu_file;
+                iter.buffer_iter[cpu_file] =
+                        ring_buffer_read_prepare(iter.tr->buffer, cpu_file);
+                ring_buffer_read_start(iter.buffer_iter[cpu_file]);
+                tracing_iter_reset(&iter, cpu_file);
         }
-
         if (!trace_empty(&iter))
                 trace_find_next_entry_inc(&iter);
         while (!trace_empty(&iter)) {
@@ -91,9 +98,10 @@ out:
 static int kdb_ftdump(int argc, const char **argv)
 {
         int skip_lines = 0;
+        long cpu_file;
         char *cp;
 
-        if (argc > 1)
+        if (argc > 2)
                 return KDB_ARGCOUNT;
 
         if (argc) {
@@ -102,8 +110,17 @@ static int kdb_ftdump(int argc, const char **argv)
                         skip_lines = 0;
         }
 
+        if (argc == 2) {
+                cpu_file = simple_strtol(argv[2], &cp, 0);
+                if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
+                    !cpu_online(cpu_file))
+                        return KDB_BADINT;
+        } else {
+                cpu_file = TRACE_PIPE_ALL_CPU;
+        }
+
         kdb_trap_printk++;
-        ftrace_dump_buf(skip_lines);
+        ftrace_dump_buf(skip_lines, cpu_file);
         kdb_trap_printk--;
 
         return 0;
@@ -111,8 +128,8 @@ static int kdb_ftdump(int argc, const char **argv)
 
 static __init int kdb_ftrace_register(void)
 {
-        kdb_register_repeat("ftdump", kdb_ftdump, "", "Dump ftrace log",
-                            0, KDB_REPEAT_NONE);
+        kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
+                            "Dump ftrace log", 0, KDB_REPEAT_NONE);
         return 0;
 }